MAX96x/MAX99x: Ultra-High-Speed, Beyond-the-Rails Comparators

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An Overview Study on Single/Dual/Quad, Ultra-High-Speed, +3V/+5V, Beyond-the-Rails Comparators

An Overview Study on Single/Dual/Quad, Ultra-High-Speed, +3V/+5V, Beyond-the-Rails Comparators

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  • Welcome to the training module on MAXIM MAX96x / MAX99x: Ultra-High-Speed, Beyond-the-Rails Comparators. This training module provides an Overview Study on Single/Dual/Quad, Ultra-High-Speed, +3V/+5V, Beyond-the-Rails Comparator family.
  • The MAX961–MAX964/MAX997/MAX999 are low-power, ultra-high-speed comparators with internal hysteresis. These devices are optimized for single +3V or +5V operation. The input common-mode range extends 100mV Beyond-the-Rails™, and the outputs can sink or source 4mA to within 0.52V of GND and VCC. Propagation delay is 4.5ns (5mV overdrive), while supply current is 5mA per comparator. The MAX961/MAX963/MAX964 and MAX997 have a shutdown mode in which they consume only 270µA supply current per comparator. The MAX961/MAX963 provide complementary outputs and a latch-enable feature. Latch enable allows the user to hold a valid comparator output. The MAX999 is available in a tiny SOT23-5 package. The single MAX961/MAX997 and dual MAX962 are available in space-saving 8-pin µMAX® packages.
  • Here list the application fields where this device can be used. It can go into single 3V to 5V conversion system, portable battery powered system, Threshold Detectors, GPS Receivers, Line Receivers, Zero-crossing detector, high speed sampling circuits.
  • This page shows in brief about different members of MAX9xx comparators along with the key specifications like no. of comparators in each package, shutdown function, Latch enable function. etc..
  • Most high-speed comparators oscillate in the linear region because of noise or undesirable parasitic feedback. This can occur when the voltage on one input is close to or equal to the voltage on the other input. These comparators have a small amount of internal hysteresis to counter parasitic effects and noise. The added hysteresis of the MAX961–MAX964/MAX997/ MAX999 creates two trip points: one for the rising input voltage and one for the falling input voltage as shown in figure. The difference between the trip points is the hysteresis. When the comparator’s input voltages are equal, the hysteresis effectively causes one comparator input voltage to move quickly past the other, thus taking the input out of the region where oscillation occurs. Standard comparators require hysteresis to be added with external resistors. The fixed internal hysteresis eliminates these resistors.
  • The MAX961/MAX963 include internal latches that allow storage of comparison results. The Latch Enable (LE) has a high input impedance. If LE is low, the latch is transparent the comparator operates as though the latch is not present. The comparator’s output state is stored when LE is pulled high. All timing constraints must be met when using the latch function.
  • The MAX9xx comparators include internal protection circuitry that prevents damage to the precision input stage from large differential input voltages. This protection circuitry consists of two groups of three front-to-back diodes between IN+ and IN-, as well as two 200Ω resistors. The diodes limit the differential voltage applied to the comparator’s internal circuitry to no more than 3V F , where V F is the diode’s forward-voltage drop.
  • The MAX961–MAX964/MAX997/MAX999 contain a current- driven output stage, as shown in Figure. During an output transition, I SOURCE or I SINK is pushed or pulled to the output pin. The output source or sink current is high during the transition, creating a rapid slew rate. Once the output voltage reaches V OH or V OL , the source or sink current decreases to a small value, capable of maintaining the V OH or V OL in static condition. This decrease in current conserves power after an output transition has occurred. One consequence of a current-driven output stage is a linear dependence between the slew rate and the load capacitance. A heavy capacitive load slows down the voltage output transition.
  • Here is an example application which is a level shifter from 3V logic to 5V logic. As shown in Figure, this circuit requires only a single comparator with an open-drain output. The circuit provides great flexibility in choosing the voltages to be translated. It also allows the translation of bipolar ±5V logic to unipolar 3V logic by using the MAX972. In that application, take care that no voltage exceeds the maximum voltage allowed on any pin and that the current into the output is limited by a sufficiently large-valued pull-up resistor.
  • The MAX961–MAX964/MAX997/MAX999’s high bandwidth requires a high-speed layout. Here list these layout guidelines.
  • Thank you for taking the time to view this presentation on MAX96x / MAX99x: Ultra-High-Speed, Beyond-the-Rails Comparators . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simple call our sales hotline. For more technical information you may either visit MAXIM site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.

Transcript

  • 1. MAX96x / MAX99x: Ultra-High-Speed, Beyond-the-Rails Comparators
    • Source: Maxim
  • 2. Introduction
    • Purpose
      • An Overview Study on Single/Dual/Quad, Ultra-High-Speed, +3V/+5V, Beyond-the-Rails Comparators .
    • Outline
      • Features
      • Applications
      • Timing Diagram
      • Input / Output Stage
      • Application circuit
    • Content
      • 12 pages
  • 3. Family Overview
    • Ultra-Fast, 4.5ns Propagation Delay
    • Ideal for +3V and +5V Single-Supply Applications
    • Beyond-the-Rails Input Voltage Range
    • Low, 5mA Supply Current (MAX997/MAX999)
    • 3.5mV Internal Hysteresis for Clean Switching
    • Output Latch (MAX961/MAX963)
    • TTL/CMOS-Compatible Outputs
    • Shutdown Mode (MAX961/MAX963/MAX964/MAX997)
    • Available in Space-Saving Packages:
      • 5-Pin SOT23 (MAX999)
      • 8-Pin μMAX (MAX961/MAX962/MAX997)
      • 16-Pin QSOP (MAX964)
  • 4. Applications
    • Single 3V/5V Systems
    • Portable/Battery-Powered Systems
    • Threshold Detectors/Discriminators
    • GPS Receivers
    • Line Receivers
    • Zero-Crossing Detectors
    • High-Speed Sampling Circuits
  • 5. Quick Selection Part Number No. of Comps. Shutdown Latch Enable Logic Output Complementary Output Supply (V) MAX961 1 Yes Yes CMOS TTL Yes 2.7 ~ 5.5 MAX962 2 No No No MAX963 2 Yes Yes Yes MAX964 4 Yes No No MAX997 1 Yes No No MAX999 1 No No No
  • 6. Timing
    • The added hysteresis of these devices creates two trip points: one for the rising input voltage and one for the falling input voltage as shown beside.
    • The difference between the trip points is the hysteresis.
  • 7. MAX961/MAX963 Timing Diagram
    • If LE is low, the latch is transparent the comparator operates as though the latch is not present.
    • The comparator’s output state is stored when LE is pulled high.
  • 8. Input Stage Circuit
    • The comparators include internal protection circuitry that prevents damage to the precision input stage from large differential input voltages.
    • This protection circuitry consists of two groups of three front-to-back diodes between IN+ and IN-, as well as two 200Ω resistors.
    • The diodes limit the differential voltage applied to the comparator’s internal circuitry to no more than 3V F , where V F is the diode’s forward-voltage drop.
  • 9. Output Stage Circuit
    • The MAX9xx devices contain a current- driven output stage.
    • During an output transition, I SOURCE or I SINK is pushed or pulled to the output pin.
    • When the output voltage reaches V OH or V OL , the source or sink current decreases to a small value, capable of maintaining the V OH or V OL in static condition.
  • 10. Application Circuit Level Shifter From 3V Logic to 5V Logic
    • It allows the translation of bipolar ±5V logic to unipolar 3V logic by using the MAX972.
    • This circuit requires only a single comparator with an open-drain output.
  • 11. Applications Information
    • Use a PCB with a good, unbroken, low-inductance ground plane.
    • Place a decoupling capacitor (a 0.1μF ceramic surface- mount capacitor is a good choice) as close to VCC as possible.
    • On the inputs and outputs, keep lead lengths short to avoid unwanted parasitic feedback around the comparators. Keep inputs away from outputs. Keep impedance between the inputs low.
    • Solder the device directly to the printed circuit board rather than using a socket.
    • For slow-moving input signals, take care to prevent parasitic feedback.
    • A small capacitor (1000pF or less) placed between the inputs can help eliminate oscillations in the transition region.
  • 12. Additional Resource
    • For ordering the MAX9xx comparators, please click the part list or
    • Call our sales hotline
    • For additional inquires contact our technical service hotline
    • For more product information go to
      • http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1481/t/al
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